[vsnet-grb-info 15799] GRB 141121A: Continued RATIR Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17087
SUBJECT: GRB 141121A: Continued RATIR Optical Observations
DATE:    14/11/23 07:05:41 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB),
Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino
Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC),
and Harvey Moseley (GSFC) report:

We observed the field of GRB 141121A (Lien et al., GCN 17075) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on
Sierra San Pedro Mártir from 2014/11 22.28 to 2014/11 22.53 UTC (26.79
to 32.94 hours after the BAT trigger), obtaining a total of 4.93 hours
exposure in the r, i and z bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS
DR9, we
obtain the following detections and upper limits (3-sigma):

 r 20.84 +/- 0.03
 i 20.68 +/- 0.03
 z > 20.02

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

The source has faded in r and i by 1.2 magnitudes or roughly t^-0.73 since
our observations on the first night (Watson et al., GCN 17084), confirming
that it is the afterglow. This fading is steeper than the t^-0.15 fading
seeing during our observations on the first night.

We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.